1956 30hp Evinrude adventures

[pro-crastinator]

Hello everyone,
The questions today revolve around the 30 HP Big twin that I have been working on since - what seems like a long time.
Carb rebuilt, new ignition parts (coils, condensors, points, wires), head gasket replaced, impellor replaced, fuel pump installed.
CYL drop test done Sunday, got fire on both cyls.
That about sums up the efforts.
I had a chance to get her out on the water this past weekend. A little chilly but it was a great time to be alive.
COuld not get speed above 15mph with the boat as light as I could manage. ( I had hoped the head gasket replacement would have improved this number)
The last thing I did was to replace the head gasket. It needed it badly and the resurfacing of the head went well.
When the head was off, there were definately scratches in the cyl wall.

I am gravitating to the possibility that the next operation should be a re-ring, cyl hone.

The purpose of this post is to get feedback from this group of experts that have guided my hands so far.
Thanks in advance.

1957 Whitehouse, 15 ft runabout - boat weight 250#?, motor weight 130#, expected speed on water ~25mph

 

[Crosbyman]

so what is the compression on the engine ??

 

[pro-crastinator]

wow. I kinda left that out. 93/95. checked and rechecked. kinda low. Does anybody think that the lower than optimal compression numbers are the
reason for the lower than desired power?
Or are my expectations too high?

 

[F_R]

That sounds low, but if it starts and idles ok, I sort of doubt that is what is robbing the top end power. Have you checked to see if it is getting water into a cylinder (or cylinders)? 15mph does sound too slow. I'd expect around 25 also.

 

[64osby]

Have you checked to see if you are dropping spark on one cylinder as you rev up?

Your description sounds like it's running in one cylinder.

 

[Crosbyman]

is the prop Ok pitch Wise ...maybe worth a try


90 pounds likely not the issue here.

 

[pro-crastinator]

Frank - I dont think water is getting into the cyl. That was a prime reason the head gasket was replaced. It needed it.
64Osby - Yep, thought that myself. This past sunday, motor idling in the lake, pulled each plug wire off and motor degraded for both. (but not at the same time lol)
Crosby - prop looks ok. havnt checked pitch but prior owners daughter skied behind this boat/motor 20 years ago or so.

SO what else is left? Did I set the point gap wrong?
It just dosent sound like its getting to the higher rpm range that you hear at a normal WOT.
After its warm, it can be slow to start as well.

Is the ring / hone job something that is unexpected for a 57 year old big twin?

I have not examined the reed valves. Are they suspect? prior opinion was that they were not.

 

[Crosbyman]

tried decarbing it to loosen up everything and increase compression....?

pulling skiers may have required a lower pitch prop if it was available in those days ??? check the prop # and pitch anyhow

but it should rev up even more on a lower pitch prop so something is not kocher


302062 filter in the glass bowl cleaned out ??? try a run without it if tank is clean

 

[pro-crastinator]

No Title

Glass bowl filter already removed - I am crazy picky about fuel quality. Tank pristine.

afterthought: COuld the Mikuni fuel pump be too low a volume?


My to do list:
Do a seafoam "treatment" to try to increase compression
Check prop pitch
Re check compression.

Thanks. Weather just turned cold again. Boat is tucked away in the garage.
Will revive this thread weeks from now after the to do list is done.

Thanks again

 

[F_R]

I know you said you replaced the head gasket. I was thinking of the exhaust cover baffle plate. They are notorious for getting a pin hole in them, allowing water to squirt into the cylinder through the exhaust ports. Of course I don't know if that is the case here, just an educated guess.

 

[pro-crastinator]

Frank, are you sayin that my to do list should include exhaust cover baffle plate removal?

As far as educated guess, thats exactly what I'm askin for.

 

[pro-crastinator]

Just thought of something,
When the head gasket was replaced and I had a chance to look down in the cyls -
I noticed something that may or may not be note worthy.
The exhaust ports were clean. And please understand I mean crazy clean - much more than I would have expected.
COuld this be evidence of water coming in?

I recall as a kid in a mechanics shop, the master mechanic would pour water down the carb while the motor was running
to dislodge carbon from the engine. Maybe Frank hit the nail on the head - again!

Exhaust cover removal is officially on the to do list.

To do list:
Wait for warmer weather.
Check ignition advance - not sure how best to do this / Should get something like 10 - 20 degrees before top dead (BTD) center at WOT.
If you have significantly less, or the ignition is after top dead center, then the motor just would not wind up.
Remove the flywheel, and when one of the points opens check where is the corresponding piston with the plug out.
Exhaust cover removal, inspect and replace gaskets.
At WOT, pump fuel bulb to see if there is any improvement. (suspect fuel pump)
Check prop pitch (standard stock prop is 10 - 3/8 dia x 12 - 1/2 pitch)
Re check compression.
Do a seafoam "treatment" to try to increase compression

 

[orbanp]

What is the RPM at wide open throttle (WOT)? The spec says that 30HP @ 4500RPM. Do you reach that RPM?
I would also check the ignition advance if you do not reach that RPM. Should get something like 10 - 20 degrees before top dead (BTD) center at WOT.
If you have significantly less, or the ignition is after top dead center, then the motor just would not wind up.
Remove the flywheel, and when one of the points opens check where is the corresponding piston with the plug out.

Good luck, Peter

 

[Crosbyman]

HIGH TRIM on AOMCI make stainless steel exhaust plates for the 7.5 hp maybe he has some for bigger engines ??

if you suspect the Mikuni (square) pump maybe you can squeeze the fuel bulb to confirm the effectiveness of the pump by assisting it a bit ...when the warm sun comes out

 

[steelespike]

I found a 59 catalog 14'10" is 300 or 325 lbs. I wonder if the link and sync is right. Does the cam pick up the carb at the right point.
I would think the motor could manage 20-25 easily.
Water may have cleaned the ports.
If the gasket is still leaking the plugs may be super clean from water intrusion as well.
I had a old Elgin that my mother cooked. Everything checked out but still water intrusion I never did solve it.

 

[pro-crastinator]

Have updated the to do list above.
Great thoughts.

Thanks much guys.

I am going to continue posting on this thread after the to do list is begun. May be a while, its mighty chilly right now (12F)
Consider that I once told my Canadian friend (Saskatchewan) that water freezes at about 50 degrees here in Atlanta.

 

[HighTrim]

I would check the exhaust plate as Frank mentioned, then ensure proper linc n sync. It is a pretty quick procedure. Is the carb butterfly open all the way at WOT? You can look at this while the motor is on the stand. Try another prop, perhaps yours is partially spun, not giving the grip on the water you require for maximum top end speed.

 

[Vintage Boat Guy]

Also try adjusting your carb, it may not be revving up because of the fuel pump being added. I would also suspect the fuel pump as I have had a similar problem and it turned out to be the fuel pump was too small.

 

[Faztbullet]

havnt checked pitch but prior owners daughter skied behind this boat/motor 20 years ago or so.

Check pitch as it would have a smaller pitch to pull a skier and that would explain low speed...

 

[pro-crastinator]

Chris - Carb butterfly valve plate is as open as it can get. Will jump on list below as soon as warmer.
VIntage - I will do the bulb pump test and answer the puel pump question. Has anybody else put a Mukini on a 30hp Big twin before?
Fazt - Will keep you posted when I can get down to check on the prop.




Current) To do list:

1. Wait for warmer weather.
2. Check ignition advance - not sure how best to do this / Should get something like 10 - 20 degrees before top dead (BTD) center at WOT.If you have significantly less, or the ignition is after top dead center, then the motor just would not wind up. Remove the flywheel, and when one of the points opens check where is the corresponding piston with the plug out.
3. Exhaust cover removal, inspect and replace gaskets. Cross fingers and hope for a crappy looking gasket seal. (potential easy fix)
4. At WOT, pump fuel bulb to see if there is any improvement. (suspect fuel pump)
5. Check prop pitch, remove and inspect prop (standard stock prop is 10 - 3/8 dia x 12 - 1/2 pitch)
6. Seafoam "treatment" may improve compression numbers